Radio device

ABSTRACT

A first reception circuit (SR 1 ) separates a signal from a desired terminal among signals from an adaptive array antenna (# 1  to # 4 ), based on a reception weight vector calculated in a reception weight vector calculator ( 20.1 ). A remodulation circuit ( 32.1 ) generates a first replica signal from a signal of a demodulated desired wave. A replica generating circuit ( 40.1 ) multiplies signals from a plurality of antennas by a weight vector for an interfering wave from a second reception circuit (SR 2 ), and generates a second replica signal corresponding to a signal from an interfering wave terminal. A reception response vector calculator ( 24.1 ) derives an impulse response of a propagation path of the signal from the desired terminal, based on the first and second replica signals.

TECHNICAL FIELD

[0001] The present invention relates to a configuration of a radioapparatus in which antenna directivity can be varied in real time, andmore particularly, to a configuration of a radio apparatus used in anadaptive array radio base station.

BACKGROUND ART

[0002] In recent years, in a mobile communication system, a variety ofmethods for allocating transmission channels have been proposed forefficient use of frequencies, of which some have been put into practicaluse.

[0003]FIG. 6 shows channel arrangements in a variety of communicationsystems: Frequency Division Multiple Access (FDMA), Time DivisionMultiple Access (TDMA), and Path Division Multiple Access (PDMA).

[0004] First, referring to FIG. 6, brief description of FDMA, TDMA andPDMA will be provided. FIG. 6(a) shows FDMA, in which analog signals ofusers 1 to 4 are transmitted in a frequency-divided manner with radiowaves of different frequencies f1 to f4, and the signals of respectiveusers 1 to 4 are separated by frequency filters.

[0005] In TDMA shown in FIG. 6(b), digitized signals of respective usersare transmitted in a time-divided manner at a certain time period (timeslot) with radio waves of different frequencies f1 to f4. The signals ofrespective users are separated by frequency filters and timesynchronization between a base station and respective user mobileterminals.

[0006] Meanwhile, a PDMA system has recently been proposed in order toimprove the efficiency of the use of radio wave frequencies as mobilephones have widely been used. As shown in FIG. 6(c), in the PDMA system,one time slot in the same frequency is spatially divided, and data of aplurality of users are transmitted. In the PDMA system, signals ofrespective users are separated, using frequency filters, timesynchronization between the base station and respective user mobileterminals, and a mutual interference eliminator such as an adaptivearray.

[0007] An operation principle of such an adaptive array radio basestation is well-known, as described in the references below.

[0008] B. Widrow, et al. : “Adaptive Antenna Systems,” Proc. IEEE, vol.55, No. 12, pp.2143-2159 (December 1967).

[0009] S. P. Applebaum: “Adaptive Arrays”, IEEE Trans. Antennas &Propag., vol. AP-24, No. 5, pp.585-598 (September 1976).

[0010]FIG. 7 is a schematic diagram conceptually showing the operationprinciple of such an adaptive array radio base station. In FIG. 7, oneadaptive array radio base station 1 includes an array antenna 2consisting of n antennas #1, #2, #3, . . . , #n, of which coverage isshown with a first hatched region 3. On the other hand, coverage ofadjacent, another radio base station 6 is shown with a second hatchedregion 7.

[0011] In region 3, a radio wave signal is communicated between a mobilephone 4, which is a terminal for a user A, and adaptive array radio basestation 1 (arrow 5). Meanwhile, in region 7, another radio wave signalis communicated between a mobile phone 8, which is a terminal foranother user B, and radio base station 6 (arrow 9).

[0012] Here, if the frequency of the radio wave signal of mobile phone 4for user A is by chance equal to that of mobile phone 8 for user B, theradio wave signal from mobile phone 8 for user B may be an unnecessary,interfering signal within region 3, depending on a position of user B,and it may cross with the radio wave signal between mobile phone 4 foruser A and adaptive array radio base station 1.

[0013] As described above, adaptive array radio base station 1 that hasreceived the crossed radio wave signals from both users A and B willoutput a crossed signal, unless the signal is subjected to some kind ofprocessing. In such a case, communication of user A, that shouldoriginally be established, will be prevented.

[0014] [Configuration and Operation of Conventional Adaptive ArrayAntenna]

[0015] In order to eliminate the signal from user B from an outputsignal, adaptive array radio base station 1 carries out a processing inthe following. FIG. 8 is a schematic block diagram showing aconfiguration of adaptive array radio base station 1.

[0016] Initially, the signal from user A is represented as A(t), and thesignal from user B is represented as B(t). Then, a reception signalx1(t) at the first antenna #1 constituting array antenna 2 in FIG. 7 isexpressed as follows.

x1(t)=a1×A(t)+b1×B(t)

[0017] Here, a1 and b1 are coefficients which vary in real time, asdescribed later.

[0018] Similarly, a reception signal xn(t) at the nth antenna #n isexpressed as follows.

xn(t)=an×A(t)+bn×B(t)

[0019] Here, an and bn are also coefficients that vary in real time.

[0020] The aforementioned coefficients, a1, a2, a3, . . . , an indicatethat there will be differences in reception intensity at respectiveantennas. This is because relative positions of antennas #1, #2, #3, . .. , #n constituting array antenna 2 are different with respect to theradio wave signal from user A respectively (for example, each antenna isarranged with a space from one another by a distance of 5 times of awavelength of the radio wave signal, that is, approximately 1 meter).

[0021] In addition, similarly, coefficients b1, b2, b3, . . . , bnindicate that there will be differences in reception intensity atrespective antennas #1, #2, #3, . . . , #n, with respect to the radiowave signal from user B. Since each user travels, these coefficientsvary in real time.

[0022] Signals x1(t), x2(t), x3(t), . . . , xn(t) received by respectiveantennas enter a reception portion 1R constituting adaptive array radiobase station 1 via corresponding switches 10-1, 10-2, 10-3, . . . ,10-n, and are provided to a weight vector control portion 11 as well asto one inputs of corresponding multipliers 12-1, 12-2, 12-3, . . . ,12-n.

[0023] Weights w1, w2, w3, . . . , wn with respect to the receptionsignals at respective antennas are applied to the other inputs of thesemultipliers from weight vector control portion 11. These weights arecalculated in real time by weight vector control portion 11, asdescribed below.

[0024] Therefore, reception signal x1(t) at antenna #1 will bew1×(a1A(t)+b1B(t)) through multiplier 12-1, reception signal x2(t) atantenna #2 will be w2×(a2A(t)+b2B(t)) through multiplier 12-2, receptionsignal x3(t) at antenna #3 will be w3×(a3A(t)+b3B(t)) through multiplier12-3, and further, reception signal xn(t) at antenna #n will bewn×(anA(t)+bnB(t)) through multiplier 12-n.

[0025] Outputs of multipliers 12-1, 12-2, 12-3, . . . , 12-n are addedin an adder 13, of which output is represented as follows.

w1(a1A(t)+b1B(t))+w2(a2A(t)+b2B(t))+w3(a3A(t)+b3B(t))+ . . .+wn(anA(t)+bnB(t))

[0026] When this representation is divided into two terms, that is, aterm relating to signal A(t) and a term relating to signal B(t), thefollowing representation can be obtained.

(w1a1+w2a2+w3a3+ . . . +wnan)A(t)+(w1b1+w2b2+w3b3+ . . . +wnbn)B(t)

[0027] Here, adaptive array radio base station 1 distinguishes betweenusers A and B, and calculates the above weights w1, w2, w3, . . . , wnso as to extract only the signal from a desired user, as describedbelow. For example, in an example of FIG. 8, weight vector controlportion 11 regards coefficients a1, a2, a3, . . . , an, b1, b2, b3, . .. , bn as constants, in order to extract only signal A(t) from user Awith which communication is to be established. Further, weight vectorcontrol portion 11calculates weights w1, w2, w3, . . . , wn such thatcoefficients for signal A(t) attain 1 as a whole, and coefficients forsignal B(t) attain 0 as a whole.

[0028] In other words, weight vector control portion 11 calculates, inreal time, such weights w1, w2, w3, . . . , wn that coefficient ofsignal A(t) attains 1 and coefficient of signal B(t) attains 0, bysolving simultaneous simple equations below.

w1a1+w2a2+w3a3+ . . . +wnan=1

w1b1+w2b2+w3b3+ . . . +wnbn=0

[0029] Though description for how to solve these simultaneous simpleequations will not be provided, it is well known as described in theaforementioned references, and has already been put into practical usein the adaptive array radio base station.

[0030] By setting weights w1, w2, w3, . . . , wn as described above, anoutput signal of adder 13 will be given as shown below.

Output signal=1×A(t)+0×B(t)=A(t)

[0031] [User Identification and Training Signal]

[0032] It is to be noted that users A and B above are distinguished inthe following manner.

[0033]FIG. 9 is a schematic diagram showing a frame configuration of aradio wave signal of a portable phone. The radio wave signal of themobile phone is mainly composed of a preamble consisting of a signalsequence already known to the radio base station, and data (such asvoice data) consisting of a signal sequence unknown to the same.

[0034] The signal sequence of the preamble includes those of informationdetermining whether or not the user is a desired user with which theradio base station should communicate. Weight vector control portion 11(FIG. 8) in adaptive array radio base station 1 compares a trainingsignal corresponding to user A, taken out from a memory 14, with thereceived signal sequence, and controls the weight vector (determinesweights) so as to extract a signal that appears to include the signalsequence corresponding to user A. The signal of user A thus extracted isoutput to the outside from adaptive array radio base station 1 as anoutput signal S_(RX)(t).

[0035] On the other hand, in FIG. 8, an external input signal S_(TX)(t)enters a transmission portion 1T constituting adaptive array radio basestation 1, and is provided to one inputs of multipliers 15-1, 15-2,15-3, . . . , 15-n. Weights w1, w2, w3, . . . , wn previously calculatedbased on the reception signal by weight vector control portion 11 arecopied and applied to the other inputs of these multipliersrespectively.

[0036] The input signals weighted by these multipliers are sent tocorresponding antennas #1, #2, #3, . . . , #n via corresponding switches10-1, 10-2, 10-3, . . . , 10-n, and transmitted to region 3 in FIG. 7.

[0037] Here, the signal to be transmitted with the same array antenna 2as used in reception is weighted, also targeted for user A as thereception signal. Therefore, the transmitted radio wave signal isreceived by mobile phone 4 for user A as if it has directivity towarduser A.

[0038]FIG. 10 visualizes such communication of the radio wave signalbetween user A and adaptive array radio base station 1. In contrast toregion 3 in FIG. 7 showing an area which the radio wave can actuallyreach, a state in which the radio wave signal is emitted withdirectivity, targeted for mobile phone 4 for user A, from adaptive arrayradio base station 1 is imaged, as shown in a virtual region 3 a of FIG.10.

[0039] In the PHS, which is a digital mobile communication system, theadaptive array as described above has already been put into practicaluse, and implementation of the PDMA system which can accommodate alarger number of users has been discussed. Such a PDMA system isdisclosed in the following references.

[0040] (1) Suzuki, Hirade, IEICE Technical Report, vol. RCS93-84,pp.37-44, January 1994

[0041] (2) S. C. Swales, M. A. Beach, D. J. Edwards, J. P. McGeehan,IEEE Trans. Veh. Technol., vol. 39, pp.56-67, Febuary 1990

[0042] (3) T. Ohgane, Y. Ogawa, and K. Itoh, Proc. VTC '97, vol. 2,pp.725-729, May 1997

[0043] As described above, in the PDMA system (Path Division MultipleAccess) using the adaptive array, an identical channel can be allocatedto a plurality of users in the same cell by adaptively directing null ofarray antenna directivity to an interfering user, so long as an optimalweight vector is calculated.

[0044] Thus, in the PDMA system, a technique to eliminate interferencein the identical channel is required. In this regard, the adaptive arrayadaptively directing null to an interfering wave is effective, becausethe interfering wave can effectively be suppressed even if the level ofthe interfering wave is higher than that of a desired wave.

[0045] When the adaptive array is used in the base station, unnecessaryemission in transmission can also be reduced, in addition to eliminatinginterference in reception.

[0046] Here, for an array pattern in transmission, an array pattern inreception may be used, or alternatively, a new array pattern may begenerated from a result of estimate of an incoming direction and thelike. The latter method is applicable, regardless of FDD (FrequencyDivision Duplex) or TDD (Time Division Duplex), however, a complicatedprocessing will be necessary. On the other hand, when the former methodis used for FDD, correction for array arrangement, weight or the likewill be needed, because array patterns are different in transmission andreception. Therefore, application for TDD is generally assumed, andsatisfactory property has been obtained in an environment where externalslots are continuous.

[0047] As described above, in the TDD/PDMA system using the adaptivearray in the base station, when an array pattern (a weight vectorpattern) obtained in an uplink is used for a downlink, and if a dynamicRaleigh propagation path with spread angle is assumed, an error rate maybe deteriorated in the downlink due to a time difference between theuplink and the downlink.

[0048] In other words, there is an interval from a time point when theradio wave is transmitted from a user terminal to the base stationthrough the uplink to a time point when the radio wave is emitted fromthe base station to the user terminal through the downlink. Therefore,an error between the emitted direction of the radio wave from the basestation and a direction in which the user terminal is actually presentwill deteriorate the error rate, when a traveling speed of the userterminal is not negligible.

[0049] As a method for estimating a weight for the downlink taking intoaccount fluctuation of such a propagation path, a technique of firstorder extrapolation using a weight vector value obtained in the uplinkhas been proposed in the following references.

[0050] (1) Katoh, Ohgane, Ogawa, Itoh, IEICE Trans., vol. J81-B-II, no.1, pp. 1-9, January 1998.

[0051] (2) Doi, Ohgane, Karasawa, IEICE Technical Report, RCS97-68,pp.27-32, July 1997.

[0052] When change over time in the weight is actually observed,however, it is not linear, and the error tends to be large with theconventional technique of the first order extrapolation of the weightvector.

[0053] In addition, in estimating the weight in transmission, it is alsonecessary to enable processing with a practical circuit scale.

DISCLOSURE OF THE INVENTION

[0054] An object of the present invention is to provide a radioapparatus which can achieve, with a practical circuit scale, suppressionof deterioration of an error rate in a downlink caused by a timedifference between an uplink and the downlink in a TDD/PDMA system byindirectly estimating a weight by estimating fluctuation over time of aresponse vector.

[0055] In order to attain such an object, a radio apparatus according tothe present invention varies antenna directivity in real time, andtransmits and receives signals to and from a plurality of terminals. Theradio apparatus includes a plurality of antennas, a first receptioncircuit, and a second reception circuit.

[0056] The plurality of antennas are arranged in a discrete manner. Thefirst reception circuit receives signals from the plurality of antennas,and separates a signal from a first terminal among the signals from theplurality of terminals. The second reception circuit receives signalsfrom the plurality of antennas, and separates a signal from a secondterminal among the signals from the plurality of terminals.

[0057] The first reception circuit i) separates the signal from thefirst terminal, based on the signals from the plurality of antennas inreceiving a reception signal, ii) generates a first replica signal basedon the separated signal from the first terminal, and calculates a firstreception correlation vector with respect to the signal from the firstterminal in accordance with the first replica signal and the signalsfrom the plurality of antennas in receiving the reception signal, iii)generates a second replica signal corresponding to the signal from thesecond terminal with the signals from the plurality of antennas, basedon separation control information for separating the signal from thesecond terminal in the second reception circuit in receiving thereception signal, and iv) estimates a reception response vector withrespect to the signal from the first terminal, based on a secondreception correlation vector with respect to the signal from the secondterminal, the first reception correlation vector, and a correlationmatrix calculated from the first and second replica signals.

[0058] According to yet another aspect of the present invention, a radioapparatus varies antenna directivity in real time, and transmits andreceives signals to and from a plurality of terminals. The radioapparatus includes a plurality of antennas, a first reception circuit,and a second reception circuit.

[0059] The plurality of antennas are arranged in a discrete manner. Thefirst reception circuit receives signals from the plurality of antennas,and separates a signal from a first terminal among the signals from theplurality of terminals. The second reception circuit receives signalsfrom the plurality of antennas, and separates a signal from a secondterminal among the signals from the plurality of terminals.

[0060] The first reception circuit includes a first reception signalseparation circuit, a first reception correlation vector calculationcircuit, a first replica signal generating circuit, and a receptionresponse vector calculation circuit.

[0061] The first reception signal separation circuit generates a firstweight vector based on the signals from the plurality of antennas andseparates the signal from the first terminal in receiving the receptionsignal. The first reception correlation vector calculation circuitcalculates, in receiving the reception signal, a first receptioncorrelation vector with respect to the signal from the first terminal,in accordance with a first replica signal, generated based on an outputof the first reception signal separation circuit, and the signals fromthe plurality of antennas. The first replica signal generating circuitgenerates a second replica signal corresponding to the signal from thesecond terminal, based on separation control information in the secondreception circuit, with respect to the signals from the plurality ofantennas in receiving the reception signal. The reception responsevector calculation circuit estimates a reception response vector withrespect to the signal from the first terminal, based on a secondreception correlation vector with respect to the signal from the secondterminal provided from the second reception circuit, the first receptioncorrelation vector, and a correlation matrix calculated from the firstand second replica signals.

[0062] Thus, according to the present invention, fluctuation over timeof the reception response vector of the adaptive array can be estimatedwith a simple circuit configuration.

[0063] In addition, another advantage of the present invention is thatdeterioration with regard to the error rate in the downlink caused bythe time difference between the uplink and the downlink can besuppressed also in the dynamic Raleigh propagation path with spreadangle or the like, by indirectly estimating fluctuation of the weight byestimating fluctuation over time of the reception response vector of theadaptive array.

BRIEF DESCRIPTION OF THE DRAWINGS

[0064]FIG. 1 is a schematic block diagram showing a configuration ofradio apparatus (radio base station) 1000.

[0065]FIG. 2 is a flowchart illustrating an overview of an operation ofradio apparatus 1000.

[0066]FIG. 3 is a diagram illustrating a timing of signal processingwhen radio apparatus 1000 operates.

[0067]FIG. 4 is a schematic block diagram showing a configuration of aradio apparatus (a radio base station) 2000.

[0068]FIG. 5 is a schematic block diagram illustrating a configurationof a transmission portion ST1 corresponding to a reception portion SR1.

[0069]FIG. 6 shows channel arrangements in a variety of communicationsystems, that is, frequency division multiple access, time divisionmultiple access, and PDMA.

[0070]FIG. 7 is a schematic diagram conceptually showing an operationprinciple of an adaptive array radio base station.

[0071]FIG. 8 is a schematic block diagram showing a configuration ofadaptive array radio base station 1.

[0072]FIG. 9 is a schematic diagram showing a frame configuration of aradio wave signal of a mobile phone.

[0073]FIG. 10 visualizes communication of the radio wave signal betweenuser A and adaptive array radio base station 1.

BEST MODE FOR CARRYING OUT THE INVENTION

[0074] In the following, embodiments of the present invention will bedescribed with reference to the drawings.

[0075] (Configuration in Which Replica Signal of Interfering Wave isGenerated from Demodulated Signal of Received Interfering Wave)

[0076]FIG. 1 is a schematic block diagram showing a configuration of aradio apparatus (a radio base station) 1000 in a PDMA base station,estimating a weight in transmission by estimating fluctuation over timeof a response vector.

[0077] As described below, in radio apparatus 1000 shown in FIG. 1,attention is paid to the fact that the weight of the adaptive array canuniquely be represented with the response vector in each antennaelement. The radio apparatus 1000 aims to suppress deterioration withregard to the error rate in the downlink caused by the time differencebetween the uplink and the downlink also in the TDD/PDMA system, byindirectly estimating the weight by estimating fluctuation over time ofthe response vector, when the dynamic Raleigh propagation path withspread angle or the like is assumed.

[0078] In the configuration shown in FIG. 1, in order to distinguishbetween users PS1 and PS2, for example, four antennas 1 to #4 areprovided.

[0079] It is to be noted that, more generally, the number of antennasmay be L (L is a natural number). For the sake of simplicity, two usersare assumed here. The present invention, however, is not limited to suchan example, and three or more users are possible. Further, in theconfiguration shown in FIG. 1, for the sake of simplicity, only aconfiguration of a portion related to signal reception is extracted forillustration. Therefore, the configuration of a transmission portionwhich is usually provided as in the configuration of a conventionaladaptive array will not be illustrated.

[0080] Radio apparatus 1000 shown in FIG. 1 includes a reception portionSR1 for separating a signal from corresponding user PS1 and a receptionportion SR2 for separating a signal from corresponding user PS2, uponreceiving signals from antennas #1 to #4.

[0081] When reception signals x1(t), x2(t), x3(t), x4(t) received atrespective antennas enter reception portion SR1, they are first providedto a synchronization circuit 2.1. After an incoming timing of the signalfrom user PS1 is detected, those signals are further provided to areception weight vector calculator 20.1 and a reception correlationvector calculator 22.1, as well as to one inputs of correspondingmultipliers 12-1.1, 12-2.1, 12-3.1, 12-4.1 respectively.

[0082] Weight coefficients wrx11, wrx21, wrx31, wrx41 with respect tothe reception signals at respective antennas are applied to the otherinputs of these multipliers from reception weight vector calculator20.1. These weight coefficients are calculated in real time by receptionweight vector calculator 20.1 as in the conventional example.

[0083] Reception portion SR1 further includes an adder 13.1 receivingand adding outputs of multipliers 12-1.1 to 12-4.1, a demodulationcircuit 30.1 receiving and demodulating an output of adder 13.1, andextracting a baseband signal, a remodulation circuit 32.1 receiving andremodulating an output of demodulation circuit 30.1, and generating areplica signal of the reception signal from user PS1, and a filteringcircuit 34.1 receiving an output of remodulation circuit 32.1 andshaping a waveform. An output of filtering circuit 34.1 is provided to atiming adjustment circuit 36.2 in reception portion SR2.

[0084] Reception portion SR1 further includes a reception correlationvector calculator 22.1 receiving reception signals x1(t) to x4(t) fromsynchronization circuit 2.1 and an output of remodulation circuit 32.1,and calculating a reception correlation vector with respect to thesignal from user PS1 in accordance with a procedure described below; anda reception response vector calculator 24.1 for calculating a receptionresponse vector with respect to the reception signal from user PS1,based on a replica signal of the signal from user PS2 obtained afteradjusting a difference in incoming timings of the reception signals ofusers PS1 and PS2 further in timing adjustment circuit 36.1 with respectto an output from filtering circuit 34.2, an output of receptioncorrelation vector calculator 22.1, and a replica signal of the signalfrom user PS1, which is the output of remodulation circuit 32.1.

[0085] Timing adjustment circuit 36.1 provides the replica signal of thesignal from user PS2 to reception response vector calculator 24.1, afteradjusting the difference in the incoming timings of the receptionsignals of users PS1 and PS2 with respect to the signal provided fromfiltering circuit 34.2 to timing adjustment circuit 36.1, in accordancewith a detection result of the incoming timings of the reception signalsof synchronization circuit 2.1 in reception portion SR1 and asynchronization circuit 2.2 in reception portion SR2.

[0086] A similar configuration is provided also for reception portionSR2.

[0087] The reason for shaping the waveform of the output fromremodulation circuit 32.2 through filtering circuit 34.2 is as follows.The incoming timings of the signals from users PS1 and PS2 are generallydifferent. Therefore, in calculating the reception response vector inreception response vector calculator 24.1, a sampling timing of thereception signal from user PS1 in reception portion SR1 is differentfrom that from user PS2 in reception portion SR2. Consequently, it isnecessary to use an interpolated signal level between sampling timingsat the output of remodulation circuit 32.2 in reception portion SR2.

[0088] As described below, by estimating fluctuation over time of theresponse vector from the reception response vector of user PS1 thuscalculated, the weight in transmission can indirectly be estimated.

[0089] [Operation Principle as Adaptive Array]

[0090] Initially, an operation of reception portion SR1 will briefly bedescribed in the following.

[0091] Reception signals x1(t), x2(t), x3(t), x4(t) received by theantenna are expressed with equations below.

x1(t)=h ₁₁ Srx ₁(t)+h ₁₂ Srx ₂(t)+n ₁(t)   (1)

x2(t)=h ₂₁ Srx ₁(t)+h ₂₂ Srx ₂(t)+n ₂(t)   (2)

x3(t)=h ₃₁ Srx ₁(t)+h ₃₂ Srx ₂(t)+n ₃(t)   (3)

x4(t)=h ₄₁ Srx ₁(t)+h ₄₂ Srx ₂(t)+n ₄(t)   (4)

[0092] Here, a signal xj(t) represents the reception signal of thejth(=1, 2, 3, 4) antenna, and a signal Srxi(t) represents a signaltransmitted by the ith (i=1, 2) user.

[0093] Further, a coefficient hji represents a complex coefficient ofthe signal from the ith user received by the jth antenna, and nj(t)represents noise contained in the jth reception signal.

[0094] Equations (1) to (4) in the above are expressed in a vectorformat as below.

X(t)=H ₁ Srx ₁(t)+H ₂ Srx ₂(t)+N(t)   (5)

X(t)=[x1(t), x2(t), . . . , x4(t)]^(T)   (6)

H _(i) =[h _(1i) , h _(2i) , . . . , h _(4i)]^(T), (i=1,2)   (7)

N(t)=[n ₁(t), n ₂(t), . . . , n ₄(t)]^(T)   (8)

[0095] It is to be noted that [. . . ]^(T) represents transpose of [. .. ] in equations (6) to (8).

[0096] Here, X(t) represents an input signal vector, H_(i) representsthe reception response vector of the ith user, and N(t) represents anoise vector, respectively.

[0097] As shown in FIG. 1, a signal synthesized by multiplying the inputsignals from respective antennas by weight coefficients wrx1i to wrx4iis output as reception signal Srxi(t).

[0098] After such preparation, for example, the adaptive array operatesin a following manner, when extracting signal Srx1(t) transmitted by thefirst user.

[0099] An output signal y1(t) of an adaptive array 100 can be expressedwith the following equations, by multiplying input signal vector X(t) bya weight vector W1.

y1(t)=X(t)W ₁ ^(T)   (9)

W₁=[wrx₁₁, wrx₂₁, wrx₃₁, wrx₄₁]^(T)   (10)

[0100] In other words, weight vector W1 is a vector having, as anelement, weight coefficient wrxj1(=1, 2, 3, 4) multiplied by jth inputsignal RXj(t).

[0101] Here, when input signal vector X(t) expressed with equation (5)is substituted in equation (9) representing y1(t), a relation in thefollowing is obtained.

y1(t)=H ₁ W ₁ ^(T) Srx ₁(t)+H ₂ W ₁ ^(T) Srx ₂(t)+N(t)W ₁ ^(T)   (11)

[0102] If the adaptive array operates in an ideal manner, weight vectorW1 is sequentially controlled with a well known technique by weightvector calculator 20.1, so as to satisfy the following simultaneousequations.

H₁W₁ ^(T)=1   (12)

H₂W₁ ^(T)=0   (13)

[0103] When weight vector W1 is completely controlled so as to satisfyequations (12) and (13), output signal y1(t) from adaptive array 1000will eventually be expressed with the following equations.

y1(t)=Srx ₁(t)+N ₁(t)   (4)

N ₁(t)=n ₁(t)w ₁₁ +n ₂(t)w ₂₁ +n ₃(t)w ₃₁ +n ₄(t)w ₄₁   (15)

[0104] In other words, signal Srxl(t) transmitted by the first user outof two users is obtained as output signal y1(t).

[0105] [Overview of Operation of Radio Apparatus 1000]

[0106]FIG. 2 is a flowchart illustrating an overview of an operation ofradio apparatus 1000.

[0107] In radio apparatus 1000, attention is paid to the fact that theweight vector (weight coefficient vector) of the adaptive array canuniquely be represented with the reception response vector in eachantenna element. The weight is indirectly estimated by estimatingfluctuation over time of the reception response vector.

[0108] First, in reception portion SR1, the propagation path of thereception signal is estimated based on the reception signal (step S100).Estimation of the propagation path is comparable to obtaining an impulseresponse of the signal transmitted from the user in equations (1) to(4).

[0109] Stated differently, in equations (1) to (4), if a receptionresponse vector H₁ can be estimated, for example, the propagation pathin receiving the signal from user PS1 can be estimated.

[0110] Succeedingly, in the transmission portion, the propagation pathin transmission, that is, the reception response vector at a time pointof transmission is predicted from the reception response vector inreception (step S102). The predicted reception response vector iscomparable to a transmission coefficient vector in transmission. Inaddition, in the transmission portion, a transmission weight vector iscalculated based on the predicted transmission coefficient vector, andthe weight in transmission is controlled (step S104).

[0111] [Operation of Reception Response Vector Calculator 24.1]

[0112] Next, an operation of reception response vector calculator 24.1in a first embodiment shown in FIG. 1 will be described.

[0113] First, four antenna elements and two users in simultaneouscommunication are assumed. Then, the reception signals at time t fromthe antennas are represented as x1(t), x2(t), x3(t), x4(t) respectively,the replica signal of the desired wave (radio wave from user PS1) isrepresented as D(t), and the replica signal of the interfering wave(radio wave from user PS2) is represented as U(t−T2). Here, a receptionresponse vector HD of the desired wave is estimated. It is to be notedthat T2 represents a difference in the incoming time between the desiredwave and the interfering wave.

[0114] Reception signal vector X(t) is expressed with the followingequations.

x1(t)=h11D(t)+h12U(t−T2)+n1(t)

x2(t)=h21D(t)+h22U(t−T2)+n2(t)

x3(t)=h31D(t)+h32U(t−T2)+n3(t)

x4(t)=h41D(t)+h42U(t−T2)+n4(t)

X(t)=[x1(t), x2(t), x3(t), x4(t)]^(T)

H_(D)=[h11, h12, h13, h41]^(T)

[0115] Here, a coefficient r11 for replica signal D(t) for user PS1 andreception signal x1(t) among the elements of the reception correlationvector is represented in the following equation. $\begin{matrix}{{r11} = {E\left\lbrack {D*(t){{xl}(t)}} \right\rbrack}} \\{= {{{h11}\quad {E\left\lbrack {D*(t){D(t)}} \right\rbrack}} + {{h12}\quad {E\left\lbrack {D*(t){U\left( {t - {T2}} \right)}} \right\rbrack}} + {E\left\lbrack {D*(t){{n1}(t)}} \right\rbrack}}}\end{matrix}$

[0116] Here, ensemble average (time average) with regard to replicasignal D(t) itself of the desired wave attains 1, while correlation ofreplica signal D(t) of the desired wave with noise signal n1(t) attains0, if the time for taking an average is sufficiently long. Therefore,following equations are established.

E[D*(t)D(t)]=0

E[D*(t)n1(t)]=0

[0117] Among the elements of the reception correlation vector,respective coefficients r21, r31, r41 for replica signal D(t) for userPS1 and other reception signals x2(t) to x4(t) can be calculated in asimilar manner.

[0118] Therefore, each element of the reception correlation vector caneventually be obtained by the calculation in the following.

r11=E[D*(t)x1(t)]=h11+h12E[D*(t)U(t−T2)]

r21=E[D*(t)x2(t)]=h21+h22E[D*(t)U(t−T2)]

r31=E[D*(t)x3(t)]−h31+h32E[D*(t)U(t−T2)]

r41=E[D*(t)x4(t)]=h41+h42E[D*(t)U(t−T2)]

[0119] Here, if the signal from user PSI is completely orthogonal tothat from user PS2, the following equation further holds.

E[D*(t)U(t−T2)]=0

[0120] In other words, if the signal from user PS 1 is completelyorthogonal to that from user PS2, reception correlation vector [r11,r21, r31, r41] will correspond to reception response vector HD for userPS1.

[0121] In actual, however, it is impossible to allocate a code sequencesuch that the signal from user PS1 is completely orthogonal to that fromuser PS2. Therefore, a value for E[D*(t)U(t−T2)] should be estimated.

[0122] Reference below discloses that, by using an inverse matrix R⁻¹ ofa correlation matrix R of users PS1 and PS2, and a correlation componentof replica signal U(t−T2) of user PS2 with reception signal vector X(t),a component of an interfering user signal is eliminated, and thereception response vector of the desired wave can be estimated:Yoshihisa Kishiyama, Takeo Ohgane, Toshihiko Nishimura, Yasutaka Ogawa,Yoshiharu Doi, “Discussion of Method for Estimating Weight for Downlinkin TDD/SDMA System Using Adaptive Array,” Technical Report of IEICE,cs99-44, RCS99-36 (1999-06), p.67-p.72.

[0123] In other words, correlation matrix R, inverse matrix R⁻¹ thereof,and the correlation component of the replica signal U(t−T2) of user PS2with reception signal vector X(t) can be expressed as below.$\begin{matrix}{R = \begin{pmatrix}{{E\left\lbrack {D*(t){D(t)}} \right\rbrack}\quad {E\left\lbrack {D*(t){U\left( {t - {T2}} \right)}} \right\rbrack}} \\{{E\left\lbrack {U*\left( {t - {T2}} \right){D(t)}}\quad \right\rbrack}\quad {E\left\lbrack {D*\left( {t - {T2}} \right){U\left( {t - {T2}} \right)}} \right\rbrack}}\end{pmatrix}} \\{R^{- 1} = \begin{pmatrix}A & B \\C & D\end{pmatrix}}\end{matrix}$

r12=E[U*(t−T2)x1(t)]

r22=E[U*(t−T2)x2(t)]

r32=E[U*(t−T2)x3(t)]

r42=E[U*(t−T2)x4(t)]

[0124] Therefore, using inverse matrix R⁻¹ of correlation matrix R andthe reception correlation vector, reception response vector HD of thedesired wave can be obtained in the following manner.

h22=Ar11+Br12

h21=Ar21+Br22

h31=Ar31+Br32

h41=Ar41+Br42

[0125] Thus, according to the configuration of radio apparatus 1000 asshown in FIG. 1, reception response vector HD of the desired wave can beestimated. In addition, the weight vector for the downlink (fortransmission) can be estimated from estimated reception response vectorH_(D) of the desired wave.

[0126]FIG. 3 illustrates a timing of signal processing when radioapparatus 1000 shown in FIG. 1 operates, based on the description above.

[0127] In FIG. 3, circles PD1 to PD6 represent the replica signal of thedesired wave, that is, the output from remodulation circuit 32.1 in FIG.1, while solid circles PU1 to PU6 represent the replica signal of theinterfering wave, that is, an output from remodulation circuit 32.2 inFIG. 1.

[0128] As described above, generally, the incoming timings of thedesired wave and the interfering wave do not match. Therefore,generally, the sampling timing for signal processing for the desiredwave in reception portion SR1 does not match that for the interferingwave in reception portion SR2.

[0129] Therefore, the output of remodulation circuit 32.2 is provided totiming adjustment circuit 36.1 after passing through filtering circuit34.2. The replica signal of the interfering wave provided from timingadjustment circuit 36.1 to reception response vector calculator 24.1 foran estimate operation of the reception response vector will attain thelevel of signal points PUI1 to PUI6.

[0130] Accordingly, with the configuration as shown in FIG. 1, it istrue that reception response vector HD of the desired wave can beestimated, but the configuration is unsatisfactory with regard to thefollowing points.

[0131] First, for both of desired wave D(t) and interfering waveU(t−T2), the replica signal needs to be remodulated after demodulation,and further to experience filtering process and timing adjustmentprocess.

[0132] In other words, the configuration of radio apparatus 1000 in FIG.1 for estimating the weight in transmission by estimating fluctuationover time of the response vector is insufficient in that an amount ofcalculation is significant, the circuit configuration is complicated,and further, the circuit scale is too large.

[0133] In addition, essentially, since a signal other than a signalsection of the interfering user (a ramp portion positioned at thebeginning of a frame, for example) does not have its data demodulated,the replica signal cannot be generated. That is, estimate accuracy ofthe response vector tends to be deteriorated for the signal sectionwhich is not subjected to demodulation process, which is unsatisfactory.

[0134] (Configuration in which Replica Signal of Interfering Wave isDirectly Generated from Reception Signal)

[0135] Therefore, in the following, a configuration of a radio apparatus2000 which can estimate reception response vector H_(D) of the desiredwave with a simpler circuit configuration will be described.

[0136]FIG. 4 is a schematic block diagram showing the configuration ofradio apparatus (radio base station) 2000 for a PDMA base station,estimating the weight in transmission by directly generating the replicasignal of the interfering wave from the reception signal to estimatefluctuation over time of the response vector.

[0137] The configuration of radio apparatus 2000 shown in FIG. 4 isdifferent from that of radio apparatus 1000 shown in FIG. 1 in thefollowing points.

[0138] First, radio apparatus 2000 includes a replica generating circuit40.1 corresponding to reception portion SR1, and a replica generatingcircuit 40.2 corresponding to reception portion SR2, instead offiltering circuits 34.1, 34.2 and timing adjustment circuits 36.1, 36.2.

[0139] As described in detail later, replica generating circuit 40.1receives reception signals x1(t), x2(t), x3(t), x4(t) fromsynchronization circuit 2.1, and multiplies those reception signals byelements of the reception weight vectors for the interfering wave fromreception weight vector calculator 20.2 in reception portion SR2respectively, to generate replica signal U(t−T2) of the interferingwave. Replica generating circuit 40.2 in reception portion SR2 basicallyoperates in a manner similar to replica generating circuit 40.1.

[0140] [Operation of Replica Generating Circuit 40.1]

[0141] Each element of reception signal vector X(t) sampled at thesampling timing for the signal of the desired user is expressed in thefollowing equations.

x1(t)=h11D(t)+h12U(t−T2)+n1(t)

x2(t)=h21d(t)+h22U(t−T2)+n2(t)

x3(t)=h31D(t)+h32U(t−T2)+n3(t)

x4(t)=h41D(t)+h42U(t−T2)+n4(t)

[0142] Here, an inner product y(t) of a weight vector W_(U)=[wu1, wu2,wu3, wu4] output from reception weight vector calculator 20.2 in orderto extract an interfering user signal in reception portion SR2 andreception signal vector X(t) is as follows. $\begin{matrix}{{y(t)} = {{{wu1x1}(t)} + {{wu2x2}(t)} + {{wu3x3}(t)} + {{wu4x4}(t)}}} \\{= {{\left( {{wu1h11} + {wu2h21} + {wu3h31} + {wu4h41}} \right){D(t)}} +}} \\{{{\left( {{wu1h12} + {wu2h22} + {wu3h32} + {wu4h42}} \right){U\left( {t - {T2}} \right)}} +}} \\{\left( {{{wu1n1}(t)} + {{wu2n2}(t)} + {{wu3n3}(t)} + {{wu4n4}(t)}} \right)}\end{matrix}$

Wu=[wu1, wu2, wu3, wu4]^(T)

[0143] Weight vector W_(U) for extracting the interfering user signal isprovided for eliminating a desired user signal. Further, if the SN ratiois sufficiently high, following equations are established because anoise component is negligible.

(wu1h11+wu2h21+wu3h31+wu4h41)=0

(wu1h12+wu2h22+wu3h32+wu4h42)=1

[0144] (wu1n1(t) + wu2n2(t) + wu3n3(t) + wu4n4(t)) ≈ 0

[0145] Eventually, inner product y(t) is obtained as follows.

y(t)=U(t−T2)

[0146] In other words, if the inner product y(t) is calculated asrequired in replica generating circuit 40.1, replica signal U(t−T2) ofthe interfering user signal can be generated.

[0147] Here, unlike the configuration shown in FIG. 1, as the replicasignal can be generated without filtering process or the like, an amountof signal processing can be reduced significantly. In addition, sincethe replica signal of the interfering user can be reproduced even in thesection where demodulation data is not present, more time is allowed forcorrelation processing, and estimate accuracy of a transmission weightcan be improved.

[0148] [Configuration of Transmission Portion]

[0149] In the following, a configuration will be described, in which thetransmission weight in transmission is estimated based on the receptionresponse vector estimated in reception portion SR1 shown in FIG. 4.

[0150]FIG. 5 is a schematic block diagram illustrating a configurationof a transmission portion ST1 corresponding to reception portion SR1.

[0151] Referring to FIG. 5, transmission portion ST1 includes atransmission coefficient vector calculator 42.1 obtaining a transmissioncoefficient vector by estimating a propagation path in transmission,that is, estimating an assumed reception response vector at atransmission time point, upon receiving reception response vector H_(D)calculated in reception response vector calculator 24.1; a memory 46.1communicating data with transmission coefficient vector calculator 42.1,and storing and holding data; a transmission weight vector calculator44.1 calculating a transmission weight vector based on an estimatedresult of transmission coefficient vector calculator 42.1; andmultipliers 15-1.1, 15-2.1, 15-3.1, 15-4.1 receiving a transmissionsignal modulated by modulation circuit 38.1 at one inputs, and havingweight coefficients wtx11, wtx21, wtx31, wtx41 applied to the otherinputs from transmission weight vector calculator 44.1, respectively.Outputs from multipliers 15-1.1, 15-2.1, 15-3.1, 15-4.1 are given toantennas #1 to #4 via switches 10-1 to 10-4.

[0152] (Estimation of Transmission Coefficient Vector)

[0153] Thus, the reception response vector with respect to the desireduser is obtained from each signal in the uplink, and based on theresult, the reception response vector for the downlink at the time pointof transmission is estimated with regression calculation or the like.

[0154] (Determination of Transmission Weight Vector)

[0155] When an estimate value for the reception response vector at thetime of transmission is obtained as described above, the transmissionweight vector can be obtained using either of three methods in thefollowing.

[0156] i) Method by Orthogonalization

[0157] A weight vector W⁽¹⁾(i)=[wtx₁₁, wtx₁₂, wtx₁₃, wtx₁₄] at time t=iT(i: natural number, T: unit time interval) of user PS1 is considered. Inorder to direct null to user PS2, following conditions are to besatisfied.

[0158] Assume the propagation path (reception response vector) predictedfor user PS2 as V⁽²⁾(i)=[h₁ ^(′(2))(i), h₂ ^(′(2))(i), h₃ ^(′(2))(i), h₄^(′(2))(i)]. Here h_(p) ^(′(q))(i) is a predicted value of the receptioncoefficient vector for the pth antenna for the qth user with respect totime i. Similarly, assume that propagation path V⁽¹⁾(i) is predicted foruser PS1 as well.

[0159] Here, W⁽¹⁾(i) is determined such that a relation ofW⁽¹⁾(i)^(T)V⁽²⁾(i)=0 is attained. As constraints, following conditions,that is, c1) and c2), are imposed.

[0160] c1) W⁽¹⁾(i)^(T)V⁽¹⁾(i)=g (a constant value)

[0161] c2) ∥W⁽¹⁾(i)∥ is minimized.

[0162] Condition c2) is comparable to minimizing a transmission power.

[0163] ii) Method Using Spurious Correlation Matrix

[0164] Here, the adaptive array consists of some antenna elements, and aportion controlling each element weight value, as described above.Generally, when the input vector of the antenna is represented as X(t),and the weight vector is represented as W, an optimal weight W_(opt)will be given in the following equation (Wiener solution), if the weightvector is controlled so as to minimize mean square error between anoutput Y(t)=W^(T)X(t) and a reference signal d(t) (MMSE standard:minimum mean square error standard).

W _(opt) =R _(xx) ⁻¹ r _(xd)   (16)

[0165] Here, the following equations have to be satisfied.

R _(xx) =E[x*(t)x ^(T)(t)]  (17)

r _(xd) =E[x*(t)d(t)]  (18)

[0166] Here, Y^(T) represents transpose of Y, Y* represents a complexregion of Y, and E[Y] represents the ensemble average. Using the weightvalue, the adaptive array generates an array pattern so as to suppressan unnecessary interfering wave.

[0167] Meanwhile, in a method using spurious correlation matrix,equation (16) in the above is calculated with spurious correlationmatrix described below.

[0168] That is, a weight vector W^((k))(i) for user k is calculated withan estimated complex reception signal coefficient h^(′(k)) _(n)(i). Whenan array response vector for the kth user is represented as V^((k))(i),the weight vector can be obtained in the following manner.$\begin{matrix}{{{V^{(k)}(i)} = \left\lbrack {{h_{1}^{\prime {(k)}}(i)},\quad {h_{2}^{\prime {(k)}}(i)}\quad,\quad \ldots {\quad,}\quad {h_{N}^{\prime {(k)}}(i)}} \right\rbrack^{T}}\quad} & (19)\end{matrix}$

[0169] Here, an autocorrelation matrix R_(xx)(i) of an assumed receptionsignal at t=iT is expressed in the following equation, using V^((k))(i).$\begin{matrix}{{R_{xx}(i)} = {{\sum\limits_{k = 1}^{K}\quad {{V^{{(k)} +}(i)}{V^{{(k)}T}(i)}}} + {NI}}} & (20)\end{matrix}$

[0170] Here, N is an assumed noise term added so that R_(xx)(i) isregular. For example, N=1.0×10⁻⁵ in the calculation in the presentinvention.

[0171] A correlation vector r_(xd)(i) of the reception signal with thereference signal is expressed in the following equation.

r _(xd)(i)=V ^((k)*)(i)   (21)

[0172] Therefore, the weight for the downlink at time t=iT can beobtained with equations (16), (20), and (21).

[0173] The inverse matrix of equation (20) can optimally be calculatedfor user k with a lemma of the inverse matrix. In the case for twousers, in particular, simple equations in the following can calculatethe weight.

W ⁽¹⁾(i)=ρ₂₂ +N)V ^((1)*)(i)−ρ₁₂ V ^((2)*)(i)   (22)

W ⁽²⁾(i)=ρ₁₁ +N)V ^((2)*)(i)−ρ₂₁ V ^((1)*)(i)   (23)

ρ_(ij) =V ^((i)) ^(H) (i)V ^((j))(i)

[0174] A method for calculating a weight vector when the autocorrelationmatrix is given in such a manner is described in the followingreferences: T. Ohgane, Y. Ogawa, and K. Itoh, Proc. VTC '97, vol. 2,pp.725-729, May, 1997; or, Tanaka, Ohgane, Ogawa, Itoh, IEICE TechnicalReport, vol. RCS98-11 7, pp.103-108, October 1998, for example.

[0175] iii) Method of Directing Beam to User PS1

[0176] When attention is paid only to directing a beam to user PS1, thefollowing equation has only to be satisfied.

W ⁽¹⁾(i)=V ⁽¹⁾(i)*

[0177] When the weight vector in transmission is determined fortransmission using any method as described above, and if a dynamicRaleigh propagation path, for example, with spread angle is assumed,deterioration with regard to the error rate in the downlink generateddue to the time difference between the uplink and the downlink also inthe TDD/PDMA system can be suppressed.

[0178] In the above description, a configuration in which thetransmission weight vector in transmission is indirectly estimated byestimating the reception response vector. Application of the estimatedreception response vector, however, is not limited to such an example.

[0179] For example, when the reception response vector is estimated, areception power of the desired wave can be calculated. Therefore, anamplitude of the transmission power can be controlled in accordance withthe reception power. In other words, by controlling the transmissionpower in accordance with a distance from the base station to the user,interference with another base station can be reduced.

[0180] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

1. A radio apparatus (2000) varying antenna directivity in real time,and transmitting and receiving signals to and from a plurality ofterminals, comprising: a plurality of antennas (#1 to #4) arranged in adiscrete manner; a first reception circuit (SR1) receiving signals fromsaid plurality of antennas, and separating a signal from a firstterminal among the signals from said plurality of terminals; and asecond reception circuit (SR2) receiving signals from said plurality ofantennas, and separating a signal from a second terminal among thesignals from said plurality of terminals; wherein said first receptioncircuit i) separates the signal from said first terminal, based on thesignals from said plurality of antennas in receiving a reception signal,ii) generates a first replica signal based on the separated signal fromsaid first terminal, and calculates a first reception correlation vectorwith respect to the signal from said first terminal, in accordance withsaid first replica signal and the signals from said plurality ofantennas in receiving said reception signal, iii) generates a secondreplica signal corresponding to the signal from said second terminalwith the signals from said plurality of antennas, based on separationcontrol information for separating the signal from said second terminalin said second reception circuit in receiving said reception signal, andiv) estimates a reception response vector with respect to the signalfrom said first terminal, based on a second reception correlation vectorwith respect to the signal from said second terminal, said firstreception correlation vector, and a correlation matrix calculated fromsaid first and second replica signals.
 2. The radio apparatus accordingto claim 1, wherein the signals transmitted and received to and fromsaid plurality of terminals are signals subjected to time divisionmultiplexing.
 3. The radio apparatus according to claim 1, wherein saidsecond reception circuit includes a reception signal separation circuit(20.2) generating a weight vector based on the signals from saidplurality of antennas, and separating the signal from said secondterminal in receiving the reception signal, and a reception correlationvector calculation circuit (22.2) calculating, in receiving saidreception signal, said second reception correlation vector, inaccordance with a third replica signal, generated based on an output ofsaid reception signal separation circuit, and the signals from saidplurality of antennas, and said reception signal separation circuitprovides said weight vector to said first reception circuit as saidseparation control information.
 4. The radio apparatus according toclaim 3, further comprising a transmission circuit (ST1) sharing saidplurality of antennas with said first and second reception circuits intransmitting and receiving signals, wherein said transmission circuitincludes a transmission propagation path estimating circuit (42.1)predicting a propagation path in transmitting a transmission signal,based on an estimated result of said reception response vectorcalculation circuit, and a transmission directivity control circuit(44.1) updating said antenna directivity in transmitting saidtransmission signal, based on an estimated result of said transmissionpropagation path estimating circuit.
 5. A radio apparatus (2000) varyingantenna directivity in real time, and transmitting and receiving signalsto and from a plurality of terminals, comprising: a plurality ofantennas (#1 to #4) arranged in a discrete manner; a first receptioncircuit (SR1) receiving signals from said plurality of antennas, andseparating a signal from a first terminal among the signals from saidplurality of terminals; and a second reception circuit (SR2) receivingsignals from said plurality of antennas, and separating a signal from asecond terminal among the signals from said plurality of terminals;wherein said first reception circuit includes a first reception signalseparation circuit (20.1) generating a first weight vector based on thesignals from said plurality of antennas and separating the signal fromsaid first terminal in receiving a reception signal, a first receptioncorrelation vector calculation circuit (22.1) calculating, in receivingsaid reception signal, a first reception correlation vector with respectto the signal from said first terminal, in accordance with a firstreplica signal, generated based on an output of said first receptionsignal separation circuit, and the signals from said plurality ofantennas, a first replica signal generating circuit (40.1) generating asecond replica signal corresponding to the signal from said secondterminal, based on separation control information in said secondreception circuit, with respect to the signals from said plurality ofantennas in receiving said reception signal, and a reception responsevector calculation circuit (24.1) estimating a reception response vectorwith respect to the signal from said first terminal, based on a secondreception correlation vector with respect to the signal from said secondterminal provided from said second reception circuit, said firstreception correlation vector, and a correlation matrix calculated fromsaid first and second replica signals.
 6. The radio apparatus accordingto claim 5, wherein the signals transmitted and received to and fromsaid plurality of terminals are signals subjected to time divisionmultiplexing.
 7. The radio apparatus according to claim 5, wherein saidsecond reception circuit includes a second reception signal separationcircuit (20.2) generating a second weight vector based on the signalsfrom said plurality of antennas, and separating the signal from saidsecond terminal in receiving the reception signal, and a secondreception correlation vector calculation circuit (22.2) calculating, inreceiving said reception signal, said second reception correlationvector, in accordance with a third replica signal, generated based on anoutput of said second reception signal separation circuit, and thesignals from said plurality of antennas, and said second receptionsignal separation circuit provides said second weight vector to saidfirst replica signal generating circuit as said separation controlinformation.
 8. The radio apparatus according to claim 7, furthercomprising a transmission circuit (ST1) sharing said plurality ofantennas with said first and second reception circuits in transmittingand receiving signals, wherein said transmission circuit includes atransmission propagation path estimating circuit (42.1) predicting apropagation path in transmitting a transmission signal, based on anestimated result of said reception response vector calculation circuit,and a transmission directivity control circuit (44.1) updating saidantenna directivity in transmitting said transmission signal, based onan estimated result of said transmission propagation path estimatingcircuit.